mmc: block: Add write packing control
The write packing control will ensure that read requests latency is
not increased due to long write packed commands.
The trigger for enabling the write packing is managing to pack several
write requests. The number of potential packed requests that will trigger
the packing can be configured via sysfs by writing the required value to:
/sys/block/<block_dev_name>/num_wr_reqs_to_start_packing.
The trigger for disabling the write packing is fetching a read request.
Change-Id: I22e8ab04cd9aca220678784c39306068a0996790
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
[merez@codeaurora.org: fixed trivial conflicts]
Signed-off-by: Maya Erez <merez@codeaurora.org>
[subhashj@codeaurora.org: fixed trivial merge conflicts]
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
[xiaonian@codeaurora.org: fix trivial merge conflict]
Signed-off-by: Xiaonian Wang <xiaonian@codeaurora.org>
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 5706053..3244d04 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -121,6 +121,7 @@
unsigned int part_curr;
struct device_attribute force_ro;
struct device_attribute power_ro_lock;
+ struct device_attribute num_wr_reqs_to_start_packing;
int area_type;
};
@@ -287,6 +288,38 @@
return ret;
}
+static ssize_t
+num_wr_reqs_to_start_packing_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+ int num_wr_reqs_to_start_packing;
+ int ret;
+
+ num_wr_reqs_to_start_packing = md->queue.num_wr_reqs_to_start_packing;
+
+ ret = snprintf(buf, PAGE_SIZE, "%d\n", num_wr_reqs_to_start_packing);
+
+ mmc_blk_put(md);
+ return ret;
+}
+
+static ssize_t
+num_wr_reqs_to_start_packing_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int value;
+ struct mmc_blk_data *md = mmc_blk_get(dev_to_disk(dev));
+
+ sscanf(buf, "%d", &value);
+ if (value >= 0)
+ md->queue.num_wr_reqs_to_start_packing = value;
+
+ mmc_blk_put(md);
+ return count;
+}
+
#ifdef CONFIG_MMC_SIMULATE_MAX_SPEED
static int max_read_speed, max_write_speed, cache_size = 4;
@@ -1918,6 +1951,47 @@
return nr_segs;
}
+static void mmc_blk_write_packing_control(struct mmc_queue *mq,
+ struct request *req)
+{
+ struct mmc_host *host = mq->card->host;
+ int data_dir;
+
+ if (!(host->caps2 & MMC_CAP2_PACKED_WR))
+ return;
+
+ /*
+ * In case the packing control is not supported by the host, it should
+ * not have an effect on the write packing. Therefore we have to enable
+ * the write packing
+ */
+ if (!(host->caps2 & MMC_CAP2_PACKED_WR_CONTROL)) {
+ mq->wr_packing_enabled = true;
+ return;
+ }
+
+ if (!req || (req && (req->cmd_flags & REQ_PREFLUSH))) {
+ if (mq->num_of_potential_packed_wr_reqs >
+ mq->num_wr_reqs_to_start_packing)
+ mq->wr_packing_enabled = true;
+ return;
+ }
+
+ data_dir = rq_data_dir(req);
+
+ if (data_dir == READ) {
+ mq->num_of_potential_packed_wr_reqs = 0;
+ mq->wr_packing_enabled = false;
+ return;
+ } else if (data_dir == WRITE) {
+ mq->num_of_potential_packed_wr_reqs++;
+ }
+
+ if (mq->num_of_potential_packed_wr_reqs >
+ mq->num_wr_reqs_to_start_packing)
+ mq->wr_packing_enabled = true;
+}
+
static u8 mmc_blk_prep_packed_list(struct mmc_queue *mq, struct request *req)
{
struct request_queue *q = mq->queue;
@@ -1947,6 +2021,9 @@
if (!(md->flags & MMC_BLK_PACKED_CMD))
goto no_packed;
+ if (!mq->wr_packing_enabled)
+ goto no_packed;
+
if ((rq_data_dir(cur) == WRITE) &&
mmc_host_packed_wr(card->host))
max_packed_rw = card->ext_csd.max_packed_writes;
@@ -2016,6 +2093,8 @@
if (phys_segments > max_phys_segs)
break;
+ if (rq_data_dir(next) == WRITE)
+ mq->num_of_potential_packed_wr_reqs++;
list_add_tail(&next->queuelist, &mqrq->packed->list);
cur = next;
reqs++;
@@ -2433,6 +2512,8 @@
goto out;
}
+ mmc_blk_write_packing_control(mq, req);
+
mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
if (req && req_op(req) == REQ_OP_DISCARD) {
/* complete ongoing async transfer before issuing discard */
@@ -2697,6 +2778,8 @@
mmc_cleanup_queue(&md->queue);
if (md->flags & MMC_BLK_PACKED_CMD)
mmc_packed_clean(&md->queue);
+ device_remove_file(disk_to_dev(md->disk),
+ &md->num_wr_reqs_to_start_packing);
if (md->disk->flags & GENHD_FL_UP) {
device_remove_file(disk_to_dev(md->disk), &md->force_ro);
if ((md->area_type & MMC_BLK_DATA_AREA_BOOT) &&
@@ -2784,6 +2867,20 @@
if (ret)
goto power_ro_lock_fail;
}
+
+ md->num_wr_reqs_to_start_packing.show =
+ num_wr_reqs_to_start_packing_show;
+ md->num_wr_reqs_to_start_packing.store =
+ num_wr_reqs_to_start_packing_store;
+ sysfs_attr_init(&md->num_wr_reqs_to_start_packing.attr);
+ md->num_wr_reqs_to_start_packing.attr.name =
+ "num_wr_reqs_to_start_packing";
+ md->num_wr_reqs_to_start_packing.attr.mode = S_IRUGO | S_IWUSR;
+ ret = device_create_file(disk_to_dev(md->disk),
+ &md->num_wr_reqs_to_start_packing);
+ if (ret)
+ goto power_ro_lock_fail;
+
return ret;
power_ro_lock_fail: